CDK9 and cancer: Cyclin-dependent kinases (CDKs) are a class of Ser/Thr protein kinases that have key roles in cell cycle regulation or cell transcription.310 CDK9 is a member of the family of CDKs and is crucial in transcription regulation that regulates most of the cancer suppressors and oncogenes.311 It overexpressed in a variety of tumors such as leukemia and malignant melanoma.